A gear-type automatic transmission used in an automobile selects a different motive power transmission path through which motive power is transmitted via gears and thus switches to one of a plurality of speed ratios by selectively engaging or disengaging a plurality of frictional engagement elements such as a clutch and a brake.
JP 2000-266173A issued by the Japan Patent Office in the year 2002 proposes that a shift shock or an internal combustion engine dynamic compression, which tend to occur as a frictional engagement element is engaged while disengaging another frictional engagement element, may be prevented by increasing the engaging oil pressure with a predetermined slope and, at the same time, reducing the disengaging oil pressure with a predetermined slope.